On Mon, 23 Feb 2009, David Wilson wrote: > So, can you fill an infinite grid with distinct integers so that any two > adjacent integers sum to a prime? > How about adding that no positive integers are omitted? Here's an example for the 4x4 case using integers 1 to 16: 11 12 5 14 6 1 2 15 7 4 3 8 16 13 10 9